Saving a major mistake...



I'm turning to you, internet people, for advice. I am making the lovely dress over there on the right, 1973 Tennis Dress.
I opted to make the longer length version, but keep the scalloped hemline. But, it wouldn't be one of my projects unless I screwed it up bigtime.

I am 90% done with this dress. The only thing that technically is left is attachment of buttons and adding button holes, but the hemline is an abomination and I'd like to save it, if possible.

I have two major mistakes that are waylaying me at the moment.
1.) I redrafted the pattern to have the full length with scalloped hem, and somehow the back center panels ended up too short. The problem is that the finished hem line is too short in the back such that wearing this dress in public would render me arrested.

2.) I forgot to redraft the bottom scallop hem facing to fit the slightly larger diameter hem line. After trying several times to attach the facing, I realized why it would not fit and figured "no big deal, I'll just hem it up."
The problem there is the hem is all puckered and looks really bad. I staystitched along the hem line and clipped the curves, hoping for an easier time hemming curved edges, but it still looks awful.

I need advice as to how to save this; everything else about it came out perfect, including altering the princess seaming to fit me. I'd hate to trash it, but right now the hemline just isn't working.

Any advice on how to add length to the center back panel and save the awful scalloped hemlines would be appreciated. I am working with a modern 2 way stretch poly fabric that is pretty forgiving when it comes to stitching removal multiple times.